Process for treating and purifying sodium chloride



Jan. 17, 1939. L. B. cARRlzo PROCESS FOR TREATING AND PURIFYING SODIUMCHLORIDE Filed Dec. 2, 1935 2 Sheets-Sheet l Jan. 17, 1939.

L. B. CARRIZO PROCESS FOR TREATING AND PURIFYING SODIUM CHLORIDE frwensflarhibmefiarr Wyn/K Patented Jan. 17, 1939 UNITED STATES PATENT OFFICEPROCESS FOR TREATING AND PURIFYING SODIUM CHLORIDE Luis BartolomCarrizo, Quilino, Argentina Application December 2, 1935', Serial No.52,519%

4 Claims. (01. 209-2) it suitable for consumption.

It is known that certain impurities commonly found in salt in itsnatural state, particularly the magnesium compounds, readily absorbmoisture and, when heated, conglomerate in the form of pellets. Theprocess according to the present invention is based upon thishygroscopic quality inherent in said impurities, with the end in view ofpurifying the sodium chloride. The process may be performed by a specialarrangement or means of comparatively simple construction and operation.

By,way of example, the attached drawings show apparatus of a. typesuitable for practicing the process of this invention.

In the drawings:

Figure 1 is a front view of a'set of kilns and a sitter used inpracticing the process of my invention;

Figure 2 is a sectional view taken substantially on line AB of Figure 1;

same reference numbers indicate the same parts.

The illustrated arrangement. or apparatus for v practicing the processof my invention comprises two similar kilns I. These kilns arepreferably formed of brickwork of fireproof material.

1 Each kiln l iscomposed of afurnace 2. and an' ash pit 3 provided withopenings 2v and 3 for feeding the kiln and discharging the ashes, re- 45spectively. These openings, which may be fitted with suitable doors,provide for internal air draught.

As may be observed in Figure 2, a horizontal partition 5 is arrangedwithin the furnace 2 having passage 6 at the back thereof, through whichthe hot'gases and the combustion smoke are conducted. Passage 6 opens atits upper end into a space or hot chamber 1, between partition 5 and thetop wall of the kiln, into which space opens mosphere. On top of thekiln I there is a heating surface 9 surrounded by a low railing orretaining wall ill.

60 Between kilns l a space is left, as maybe seen Figure 3 is a sideview of the sifter, on an en In the different figures of thedrawingsythe a stack 8 for creating a draft through furnace 2 and space1, this stack discharging into the atin Figures 1 and 5, which spaceaccommodates the sifting machine, illustrated more fully in Figures 3,4, 6 and 7.

The sifting machine comprises a hopper II from which troughs l2 extendupward to the tops of the kilns I, adjacent the heating sur-' faces 9thereof.

Hopper H is arranged on a. scaffold l3 and communicates with the upperend of a casing mounted on thescaifold at an inclination downward andforward thereof, by means of flexible rods J5.

For the purpose of imparting a reciprocating motion to casing I4, Iprovide a shaft IS on which is secured an eccentric l1 connected by arod II! to casing l4 beneath the latter. Shaft I6 is journaled insuitable bearings on the scaffold i3 and is provided at one end with apair of pulleys l9 and 20, -one being fast to the shaft and the otherloose thereon, adapted to be driven through an endless belt inconnection with a motor (not shown), providing a drive of known type.Any

other suitable means may be provided for rotatmovement may be impartedto the shaft by hand power, by arranging a crank on one end of theshaft, in a known manner which need not be illustrated.

Within thecasing l4 (see Figure 6) there are conveniently arranged acoarse mesh sieve 2i and a fine mesh sieve 22, the latter being placedbeneath sieve 2|. If desired,'additional sieves of increasingly finermesh downward, in accordance with the different degrees of fineness ofsalt it is desired to obtain, may be provided,- as will be readilyunderstood from the following explanation, and which need not beillustrated.

The sieves 2| and 22 divide the casing it into three compartments orchambers havingat the front thereof, respectively, outlets'23, Hand 25,

the first outlet 23 being for theiimpuritiescommonly termed tailings,the second outlet 24 being for the sodium chloride in small lumps, and

the third outlet 25 being for sodium-chloride in finely powdered form.

The, process in acc rdance with this invention is'asfollowst The crudesalt which is extracted from the salines, is first passed through agrinding mill of known type. If the salt is already available in a moreor less divided state, grinding may be dispensed with.

In order to expel the moisture and cause the formation of theconglomerates of the impurities contained in the sodium chloride, thecrude salt, which has previously been ground, when necessary, is appliedto the heating surfaces 9 of the kilns l which surfaces are suitablyheated, striving to hold their temperature between 80 and 100centigrade.

By spreading the salt upon the surfaces 9 and agitating it by means of arate or any other suitable tool, the water contained therein will beexpelled by evaporation, while simultaneously the impurities will absorba portion of the water and form pellets, by virtue of their hygroscopiccharacter referred to thus forming the tailings. When this operation hasbeen completed, the salt is transferred, conveniently by means of therakes or other tools, to the troughs l2, and by, the latter, to thehopper I I, whence it passes into the casing ll onto sieve 2 I.

The impurities or tailings which, on account of their conglomeration,will not pass through the sieve 2|, are discharged through the outlet23, whereas the particles of sodium chloride readily pass through saidsieve 2| and fall upon the sieve 22, which is of fine mesh. The more orless coarse grained salt will be discharged through outlet 24, while thesalt in finely powdered form, which passes through the fine mesh sieve22, will be discharged through outlet 25. In order to facilitate themovement of the salt and prevent clogging of the sitter, the casing I4is reciprocated in the manner previously described.

At the respective outlets 23, 24, and 25, suitable containers may beprovided for collecting the materials issuing therefrom. The tailingsdischarged from outlet 23 may be rejected, and the sodium chloridedischarged from outlets 24 and 25 may be suitably packed fortransportation and sale.

The sodium chloride is thus collected in almost a chemically pure state,the originally contained impurities having been eflectivelyseparatedtherefrom by the combined action of heating and agitation, withaccompanying conglomeration of the impurities, during the drying processto which the crude salt extracted from the mines is subjected.

' In the following is given, by way of illustration only, an analysis of100 grams crude salt extracted from Salinas Grandes (Province ofCordoba, Argentine Republic) in order to establish the ingredientsforming conglomerations and the quantity of sodium chloride which isobtained:

100 grams crude salt, dfledpcontains Grams Water 0. 00000 Insolubleinorganic matters 0.05760 Insoluble organic matters 0. 4011 Calciumsulphate (CaSO) 0.09977 Magnesium sulphate (MgSO4) 0. 00452 Sodiumsulphate (NazSOO 0.47592 Sodium chloride (NaCl) 99. 31242 Nondeterminedmatter 0.00925 kilns i, forming pellets which are easily separated inthe sifting operation, in such manner as to obtain the sodium chloridein a pure state, the particles of foreign substances which succeed ingetting past the sieves and mixing with the salt proper forming aninfinitesimal quantity which may be disregarded.

Modifications may be introduced without departing from the scope of thepresent invention, as defined in the appended claims.

I claim:

1. The process of treating a mixture of sodium chloride and hygroscopicimpurities for removal of the latter from the sodium chloride, whichcomprises heating the mixture to a maximum temperature of approximately100 C. and drying the' sodium chloride by the combined action of heatand absorption of moisture by the hygroscopic impuritieswhilegconglomerating the latter in the form of pellets, and separatingthe dried sodium chloride from the pellets of conglomerated impurities.

2. The process of treating a mixture of sodium chloride and hygroscopicimpurities for removal of the latter from the sodium chloride, whichcomprises spreading the mixture in a relatively thin layer upon aheating surface, there heating the mixture to approximately 80 C. whilestirring it, thereby drying the sodium chloride by the combined actionof heat and absorption of moisture by the hygroscopic impurities whileconglomerating the latter in the form of pellets, and separating thedried sodium chloride from the pellets of conglomerated impurities.

3. The process of treating a mixture of sodium chloride and hygroscopicimpurities for removal of the latter from thesodium chloride, whichcomprises spreading the mixture in a relatively thin layer upon aheating surface, there heating the mixture to a temperature ofapproximately 100 C. while stirring it, thereby drying the sodiumchloride by the combined action of heat and absorption of moisture bythe hygroscopic impurl ties while conglomerating the latter in the formof pellets, and separating the dried sodium chloride from the pellets ofconglomerated impurities.

4. The process of treating a mixture of sodium chloride and hygroscopicimpurities for removal of the latter from the sodium chloride, whichcomprises spreading the mixture is a relatively thin layer upon aheating surface, there heating the mixture to a temperature betweenapproximately 80 and 100 C. while stirring it, thereby drying the sodiumchloride by the combined action of heat and absorption of moisture bythe hygroscopic impurities while conglomerating the latter in the formof pellets, and separating the dried sodium chloride from the pellets ofconglomerated impurities.

t LUIS BARTOLOME CARRIZO.

